Bump shipmonk/dead-code-detector from 1.1.3 to 1.2.0 in /.dev-tools

Bumps [shipmonk/dead-code-detector](https://github.com/shipmonk-rnd/dead-code-detector) from 1.1.3 to 1.2.0.
- [Release notes](https://github.com/shipmonk-rnd/dead-code-detector/releases)
- [Commits](shipmonk-rnd/dead-code-detector@1.1.3...1.2.0)

---
updated-dependencies:
- dependency-name: shipmonk/dead-code-detector
  dependency-version: 1.2.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.dev-tools/composer.json

@@ -13,7 +13,7 @@
         "phpstan/phpstan-phpunit": "^2.0.16",
         "phpstan/phpstan-strict-rules": "^2.0.11",
         "shipmonk/composer-dependency-analyser": "^1.8.4",
-        "shipmonk/dead-code-detector": "^1.1.3",
+        "shipmonk/dead-code-detector": "^1.2.0",
         "shipmonk/phpstan-rules": "^4.4.0",
         "squizlabs/php_codesniffer": "^4.0.1",
         "tomasvotruba/type-coverage": "^2.2.1",